Rolling bearings

Abstract

To provide a rolling bearing having excellent in an oil film formation capacity in a sliding part between a circumferential surface of a bearing ring and a guide surface of a holder.SOLUTION: The combined roughness of a circumferential surface 10 of one of an outer bearing ring 1 and an inner bearing ring 2 and a guide surface 12 of a holder 4 is 0.7 μm or less, and the circularity of the circumferential surface 10 is 30 μm or less, so that it is possible to increase oil film parameters on a sliding part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rolling bearing having a raceway guided cage. [Background technology]

[0002] Methods of guiding the cage radially can be broadly divided into two types: a rolling element guide method in which the rolling elements slide between the inner surface of the cage pocket and the rolling elements, and a raceway guide method in which the circumferential surface of either the inner or outer raceway ring slides against the guide surface of the cage.

[0003] In the bearing ring guide system, a guide clearance is set between the guide surface of the cage and the circumferential surface of the bearing ring. If the eccentricity of the cage relative to the bearing ring exceeds the range of the guide clearance, the guide surface of the cage slides circumferentially relative to the circumferential surface of the bearing ring. At this time, the sliding portion between the mating surface of the cage and the circumferential surface of the bearing ring is lubricated by oil present inside the rolling bearing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-169766 Summary of the Invention [Problem to be solved by the invention]

[0005] In a cage with a raceway guide system, if the combined roughness of the circumferential surface of the raceway ring and the guide surface of the cage is large, it is difficult for an oil film to form in the sliding area between the circumferential surface of the raceway ring and the guide surface of the cage, especially when the rolling bearing is rotating at low speeds, and this sliding resistance creates resistance to the rotation of the rolling bearing.

[0006] Furthermore, if the circumferential surface of the bearing ring, which is made of a hard material, has a high surface roughness, when the oil film breaks down in the sliding portion, it will be highly aggressive to the guide surface of the cage, leading to early damage to the guide surface.

[0007] In addition, a wedge-shaped gap is formed between the guide surface of the cage and the circumferential surface of the raceway ring, which gradually narrows in the circumferential direction toward the sliding portions on both sides. This has the effect of promoting oil film formation in the sliding portions due to the wedge action when oil is dragged circumferentially into the wedge-shaped gap, but if the circularity and roughness of the circumferential surface of the raceway ring are not appropriate, an oil film will not form in the sliding portions, causing solid contact on both sides, further increasing sliding resistance and raising the risk of early damage.

[0008] In view of the above background, the problem to be solved by the present invention is to provide a rolling bearing having excellent oil film formation capability at the sliding portion between the circumferential surface of the raceway and the guide surface of the cage. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a rolling bearing comprising an outer raceway ring having an outer raceway surface, an inner raceway ring having an inner raceway surface, a plurality of rolling elements arranged between the outer raceway surface and the inner raceway surface, and a cage that maintains the circumferential spacing of the plurality of rolling elements, wherein one of the outer raceway ring and the inner raceway ring has a circumferential surface that guides the cage, and the cage has a plurality of pocket inner surfaces that hold the rolling elements and a guide surface that is guided by the circumferential surface, wherein the composite roughness of the circumferential surface and the guide surface is 0.7 μm or less, and the roundness of the circumferential surface is 30 μm or less.

[0010] According to the above configuration, the composite roughness of the guide surface and circumferential surface, which greatly affects the sliding resistance and aggressiveness of the guide surface of the cage and the circumferential surface of the raceway, and the roundness of the circumferential surface of the raceway, are reduced to 0.7 μm or less, and the roundness of the circumferential surface is reduced to 30 μm or less, thereby increasing the oil film parameters at the sliding parts on both sides and achieving excellent oil film formation ability.

[0011] This invention is suitable for a cage having an annular portion and two or more claw portions circumferentially spaced apart and protruding from the annular portion in one axial direction, with pockets formed between adjacent claw portions in the circumferential direction to accommodate the rolling elements. Because the claw portions of this type of cage are cantilevered, they are more susceptible to deformation by centrifugal force than squirrel-cage cages in which two annular portions are separated by pillar portions, and the guide clearance between the guide surface of the cage and the circumferential surface of the raceway ring is more likely to narrow and change with high-speed rotation. By setting the composite roughness and the roundness of the circumferential surface small as described above, it is possible to prevent oil film breakdown and early damage to the sliding portion even during high-speed rotation.

[0012] The cage may further include a locking member disposed in the other axial direction relative to the cage so as to restrict movement of the cage in the other axial direction, the annular portion having a back surface facing the locking member in the axial direction, the annular portion and each of the claw portions being integrally formed by injection molding, and the injection molding gate being disposed in a portion of the surface of the cage excluding the guide surface and the back surface. Restricting movement of the cage in the other axial direction with the locking member reduces the protruding height of the claw portions, thereby suppressing deformation of the cage due to centrifugal force. Furthermore, forming the annular portion and each of the claw portions integrally by injection molding provides excellent mass productivity for the cage. The position of the injection molding gate corresponds to the position of a gate mark on the surface of the cage, but burrs may occur at the gate mark during mold release. If the gate is positioned in a location other than the guide surface and back surface of the cage, even if burrs occur in the gate marks on the cage, when the cage is guided by the raceway or the back surface of the cage with short claws is received by a locking member to restrict movement, the burrs in the gate marks will not rub against the circumferential surface of the raceway or the locking member, and will not increase the rotational torque of the rolling bearing or cause noise or vibration.

[0013] When considering the protruding height of the claw portions relative to the annular portion in one axial direction, it is preferable that the difference in protruding height between each of the claw portions be within 120 μm. Among the multiple claw portions, a claw portion with an excessively large protruding height may increase the sliding area with the rolling element, which is undesirable for reducing the rotational torque of the rolling bearing, while a claw portion with an insufficient protruding height may not be able to adequately hold the rolling element, which is undesirable. To avoid these problems, it is preferable that the difference in protruding height between each of the claw portions be kept to within 120 μm.

[0014] Preferably, the composite roughness of the inner surface of the pocket of the cage and the surface of the rolling element held in the inner surface of the pocket is less than 0.51 μm, which can mitigate an increase in sliding resistance between the inner surface of the pocket and the surface of the rolling element and suppress heat generation.

[0015] The variations in the outer diameter and the inner diameter of the cage are preferably each within 600 μm. By reducing the variations in the outer diameter and the inner diameter of the cage in this manner, runout during rotation of the cage can be suppressed.

[0016] For example, the cage can be made of polyamide resin. As mentioned above, if the composite roughness of the guide surface of the cage and the circumferential surface of the raceway ring and the roundness of the circumferential surface are set small, heat generation due to sliding resistance between the guide surface and the circumferential surface and attack of the circumferential surface against the guide surface can be suppressed, so even if polyamide resin, which has inferior heat resistance compared to super engineering plastics, is used as the cage material, it is possible to make a cage that can withstand use at high speeds.

[0017] It is preferable that the oil lubricating the cage has a kinematic viscosity of 50 cst or less at 40°C. If the kinematic viscosity of the oil is high, the agitation resistance of the oil caused by the cage and rolling elements increases, making the rolling bearing more susceptible to temperature rise and reducing energy efficiency. If the cage is lubricated with low-viscosity oil, with a kinematic viscosity of 50 cst or less at 40°C, the agitation resistance of the oil inside the bearing can be reduced.

[0018] The rolling bearing according to the present invention is suitable for applications in which it supports a rotating shaft included in a motor or a transmission connected to a motor. As described above, the rolling bearing according to the present invention has excellent lubrication properties for the sliding parts when the cage is guided by the raceways, and is therefore suitable for high-speed rotation applications such as the rotating shaft of a motor.

[0019] Here, a motor refers to at least one of an electric device that converts electrical energy to output rotation as a drive source, and an electric device that converts input rotation into electrical energy. A transmission refers to a device that converts the input rotational speed and transmits it to the output side, and is a concept that encompasses continuously variable transmissions in which the speed conversion ratio (reduction ratio, gear ratio) is continuously variable, and fixed-ratio transmissions in which the speed conversion ratio is fixed. Fixed-ratio transmissions include speed reducers or speed increasers in which there is only one speed conversion ratio. [Effects of the Invention]

[0020] As described above, by adopting the above configuration, the present invention can increase the oil film parameter at the sliding portion between the circumferential surface of the raceway ring and the guide surface of the cage, thereby making it possible to create a rolling bearing with excellent oil film formation ability. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a half cross-sectional view showing a rolling bearing according to an embodiment of the present invention. [Figure 2] FIG. 1 is a partial perspective view showing a rolling bearing according to an embodiment, with a portion cut away; [Figure 3] 1 is a perspective view of a cage according to an embodiment; [Figure 4] 1 is a cross-sectional view of a cage according to an embodiment; [Figure 5] Right side view of the cage in Figure 4 [Figure 6] Schematic diagram showing an example of use of a rolling bearing according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of a rolling bearing according to the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0023] The rolling bearing shown in Figures 1 and 2 comprises an outer raceway 1, an inner raceway 2 arranged coaxially with the outer raceway 1, a plurality of rolling elements 3 arranged between these raceways 1 and 2, and a cage 4 that maintains the circumferential spacing of these rolling elements 3.

[0024] Here, the direction along the central axis when the central axes of the inner and outer raceways 1 and 2 and the cage 4 are aligned is referred to as the "axial direction." The direction along the circumference around the central axis is referred to as the "circumferential direction." The direction perpendicular to the central axis is referred to as the "radial direction." The inner and outer diameters refer to the diameters of an imaginary inscribed circle or imaginary circumscribed circle that is concentric with the central axis. The direction radially away from the central axis is referred to as the radially outer side, and the direction radially closer to the central axis is referred to as the radially inner side. In FIG. 1, the central axes of the inner and outer raceways 1 and 2 and the cage 4 are aligned, and the left-right direction in FIG. 1 corresponds to the axial direction, with one axial direction being the right and the opposite axial direction being the left. In FIG. 1, the radial direction corresponds to the up-down direction.

[0025] Outer race 1 is an annular bearing component having an inner circumference with an outer raceway 5. Inner race 2 is an annular bearing component having an outer circumference with an inner raceway 6.

[0026] The rolling elements 3 are balls. A plurality of rolling elements 3 are interposed between an outer raceway surface 5 and an inner raceway surface 6. Each raceway surface 5, 6 is formed with a raceway groove having an arc-shaped cross section. A deep groove ball bearing is shown in the figure.

[0027] The cage 4 is an annular bearing component that holds the plurality of rolling elements 3 so that they are evenly spaced in the circumferential direction. The cage 4 holds the plurality of rolling elements 3 so that they are evenly spaced in the circumferential direction.

[0028] One of the outer raceway ring 1 and the inner raceway ring 2 is fixed to rotate integrally with a rotating shaft (not shown), and the other is fixed to a housing (not shown) that is stationary relative to the rotating shaft.

[0029] The inside of the rolling bearing is lubricated with oil. The oil may be liquid oil supplied from outside the bearing, or may be the base oil of grease placed inside the bearing.

[0030] The inner and outer raceways 1 and 2 and the rolling elements 3 are each made of steel.

[0031] As shown in FIGS. 3 to 5, the cage 4 has an annular portion 7 that is continuous around the entire circumference, and two or more claw portions 8 that are spaced apart in the circumferential direction and protrude from the annular portion 7 in one axial direction.

[0032] The spaces between the claws 8 facing each other in the circumferential direction form pockets 9 that house the rolling elements 3. The pockets 9 are spaces that allow the rolling elements 3 to move freely relative to the cage 4.

[0033] The pockets 9 are open to the radially outer side, the radially inner side, and one axial side of the cage 4. The rolling elements 3 can be accommodated in the pockets 9 through one axial opening of the pockets 9.

[0034] As shown in Figures 1 and 2, one of the outer raceway ring 1 and the inner raceway ring 2 has a circumferential surface 10 that guides the cage 4. The circumferential surface 10 is located axially on the other side of the raceway surface 6 of the one raceway ring 2, and extends along the circumferential direction all around.

[0035] The circumferential surface 10 in the illustrated example is formed into a cylindrical surface that defines the outer diameter of one of the bearing rings 2 .

[0036] The cage 4 has a plurality of pocket inner surfaces 11 that hold the rolling elements 3, and a guide surface 12 that is guided by the circumferential surface 10.

[0037] The guide surface 12 is a surface portion that faces the circumferential surface 10 in the radial direction with a radial guide gap therebetween. When the cage 4 is eccentric with respect to one of the raceways 2 by more than the guide gap, the guide surface 12 and the circumferential surface 10 slide relative to each other in the circumferential direction. This sliding causes the cage 4 to be guided in the radial direction by one of the raceways 2. In the illustrated example, the guide surface 12 is formed into a cylindrical surface that defines the inner diameter of the annular portion 7.

[0038] The composite roughness of the guide surface 12 and the circumferential surface 10 is 0.7 μm or less. Here, if the composite roughness is σ, then σ=√(Rq1 2 +Rq2 2 ) where Rq1 is the root mean square roughness of the guide surface 12. Rq2 is the root mean square roughness of the circumferential surface 10. Here, the root mean square roughness is the value (μm) of the root mean square roughness Rq specified in JIS (Japanese Industrial Standards B0601:2013). The arithmetic mean roughness Ra and the root mean square roughness Rq specified in the JIS have a correlation such that Rq = 1.25Ra.

[0039] The lubrication mode at the sliding interface between the guideway surface 12 and the circumferential surface 10 can be evaluated based on the value of the oil film parameter Λ = h / σ. Here, h is the minimum oil film thickness (μm) at the sliding interface between two surfaces with a composite roughness σ. If Λ ≥ 3, the sliding interface is considered to be hydrodynamic lubrication, where the two surfaces are completely separated by an oil film. If Λ < 3, the sliding interface is considered to be boundary lubrication or mixed lubrication, where the two surfaces are in microscopic solid contact. Note that the sliding interface between the circular guideway surface 12 and the circumferential surface 10 can be considered a contact ellipse in elastohydrodynamic lubrication theory, and the minimum oil film thickness h can be calculated based on this theory.

[0040] By setting the composite roughness σ of the guide surface 12 and the circumferential surface 10 to 0.7 μm or less, it becomes possible to achieve an oil film parameter Λ≧3 even when the inside of the rolling bearing is lubricated with a low-viscosity oil (not shown) that is recommended for motor shafts, transmissions, differentials, etc., even when the rolling bearing is rotating at low speeds.

[0041] The circularity of the circumferential surface 10 is 30 μm or less. Here, the circularity is the value of the difference in radius between two concentric geometric circles when the distance between the two concentric circles is smallest when any circumference passing through the circumferential surface 10 is sandwiched between them. In other words, the difference in radial distance between the central axis and the radially outermost point on the entire surface of the circumferential surface 10 that slides against the cage 4 in the circumferential direction is 30 μm or less. By providing the circumferential surface 10 with such a small circularity, it is possible to avoid excessive local narrowing between the guide surface 12 and the circumferential surface 10, which would result in high contact pressure between the two surfaces. This reduces the aggressiveness of the circumferential surface 10 made of a hard metal against the guide surface 12. Furthermore, it is possible to ensure that the oil film parameter Λ≧3 holds regardless of the position on the circumferential surface 10 where the guide surface 12 slides during low-speed rotation of the rolling bearing.

[0042] That is, a wedge-shaped gap is formed at the sliding portion between the guide surface 12 and the circumferential surface 10, which gradually narrows in the radial direction as it approaches the circumferential direction. When the oil is drawn into the wedge-shaped gap, a wedge action generates fluid pressure in the oil, and when the relative peripheral speed in the circumferential direction between the guide surface 12 and the circumferential surface 10 is equal to or greater than a certain value, the oil film parameter Λ≧3 holds, and the guide surface 12 and the circumferential surface 10 are in a fluid lubricated state.

[0043] An example of a low-viscosity oil that lubricates the inside of the bearing, including the cage 4, is an oil with a kinematic viscosity of 50 cst or less at 40°C. Here, the kinematic viscosity is a value measured in accordance with the kinematic viscosity testing method specified in JIS (K2283:2000). By using such a low-viscosity oil, the agitation resistance of the oil inside the bearing can be reduced.

[0044] An example of an oil having a kinematic viscosity of 50 cst or less at 40° C. is an oil equivalent to VG46 or less in the ISO viscosity classification. Preferably, an oil equivalent to VG32 or less in the ISO viscosity classification is used.

[0045] When using a low-viscosity oil such as that described above, it is preferable to set the composite roughness σ of the guideway surface 12 and the circumferential surface 10 and the roundness of the circumferential surface 10 to values ​​that will establish the oil film parameter Λ ≧ 3 when the relative circumferential speed between the two surfaces reaches 100 m / s. This circumferential speed is reached in a short time after the rolling bearing starts to rotate, so it is possible to quickly transition to a state where Λ ≧ 3 is established.

[0046] The pocket inner surface 11 is a surface portion that defines a pocket gap between the rolling elements 3 and the cage 4, which determines the amount of free movement of the rolling elements 3 relative to the cage 4. Therefore, the pocket inner surface 11 can come into contact with the rolling elements 3.

[0047] When the rolling bearing rotates, the cage 4 rotates and is deformed by the centrifugal force. If the centrifugal force becomes strong, each claw 8 tilts radially outward, causing the annular portion 7 to deform in a twisted manner. This deformation affects the pocket inner surface 11, reducing the pocket clearance. If the pocket clearance becomes negative, the pocket inner surface 11 interferes with the rolling elements 3, causing them to come into abnormally strong contact. Increasing the pocket clearance will deteriorate the acoustic characteristics. To maintain acoustic characteristics at a practical level during high-speed rotation, it is preferable to set the pocket clearance to 0.5 mm or less.

[0048] As shown in Figures 3 to 5, the pocket inner surface 11 in the illustrated example is made up of a pair of end face portions 13, 13 formed on circumferentially facing sides of circumferentially adjacent claw portions 8, 8, and a pocket bottom face portion 14 formed on one axial side surface of the annular portion 7. To prevent the pair of end face portions 13, 13 from coming into abnormally strong contact with the rolling element 3 so as to hold it when the claw portions 8 are tilted due to centrifugal force, the end face portion 13 of each claw portion 8 is shaped so as not to be able to engage with the rolling element 3 in the axial and radial directions. For example, the pair of end face portions 13, 13 can each be made flat in the axial and radial directions, or the pair of end face portions 13, 13 can ... parallel to each other and flat in the axial direction.

[0049] The pocket bottom portion 14 is a flat surface extending in the radial and circumferential directions.

[0050] The protruding height of the claw portion 8 in one axial direction relative to the annular portion 7 is defined as H. The protruding height H corresponds to the distance between an imaginary radial plane that contacts the tip of the claw portion 8 and an imaginary radial plane that contacts the bottom of the pocket 9. The tip of the claw portion 8 is the part of the claw portion 8 that is located furthest in one axial direction. The bottom of the pocket 9 is the part of the pocket inner surface 11 that is located furthest in the other axial direction, which is on the pocket bottom surface portion 14 in the illustrated example.

[0051] The difference in protrusion height H between each of the claw portions 8 is within 120 μm. Here, the difference in protrusion height H between each of the claw portions 8 means the difference between the maximum protrusion height and the minimum protrusion height among the plurality of claw portions 8.

[0052] To prevent the rolling elements 3 from climbing over the claw portions 8 during high-speed rotation of the rolling bearing, the height H is set to 0.15d≦H. On the other hand, the smaller the protrusion height H, the less the claw portions 8 are affected by centrifugal force. Setting H≦0.65d makes it possible to reduce the weight of the claw portions 8 and make them less susceptible to the effects of centrifugal force.

[0053] If H≦0.65d is set so that the pocket inner surface 11 is shaped so that it cannot axially engage with the rolling elements 3, it will be difficult to sufficiently prevent the retainer 4 from coming out by the engagement between the claws 8 and the rolling elements 3. In order to prevent the retainer 4 from coming out, the rolling bearing shown in Figures 1 and 2 further comprises a locking member 15 that is arranged on the other axial side relative to the retainer 4 so as to restrict movement of the retainer 4 in that other axial direction.

[0054] The locking member 15 is an annular sealing member attached to the circumferential groove of the outer raceway 1. While an example has been shown in which the locking member 15 uses a seal made of a core metal and an elastic material including a seal lip, it is also possible to use a shield made of a metal plate or a locking member specifically designed to restrict the cage. The locking member may also be attached to the inner raceway.

[0055] A back surface 16 that faces the locking member 15 in the axial direction is formed on the other axial side surface of the annular portion 7. A clearance is set between the locking member 15 and the back surface 16. When the cage 4 attempts to come off in the other axial direction relative to the plurality of rolling elements 3, the back surface 16 of the cage 4 is received in the axial direction by the locking member 15, and the cage 4 slides at the back surface 16 in the circumferential direction relative to the locking member 15.

[0056] Each sliding portion between the locking member 15 and each of the other components such as the cage 4 and the raceway 2 can also be made to transition to fluid lubrication. That is, two or more protrusions are formed in a circumferential direction on one of the two surfaces constituting each sliding portion, and the other surface is made to be a surface along the circumferential direction, forming a wedge-shaped gap between the protrusions and the other surface, and the wedge action when the protrusions drag oil between adjacent protrusions in the circumferential direction and the other surface promotes oil film formation.

[0057] The realization of fluid lubrication by the locking members and projection rows as described above is a technique disclosed in Patent Document 1 and the like, and therefore detailed illustrations and explanations thereof will be omitted.

[0058] The composite roughness σ of the pocket inner surface 11 of the cage 4 and the surfaces of the rolling elements 3 held in said pocket inner surface 11 is less than 0.51 μm. The surfaces of the rolling elements 3 roll on the inner and outer raceway surfaces 5, 6 and are rolling surfaces that are received circumferentially by the pocket inner surface 11 to maintain the circumferential spacing between the rolling elements 3. The surfaces of the rolling elements 3 slide against the pocket inner surface 11 in the rolling direction of the rolling elements 3. By making the composite roughness σ of the pocket inner surface 11 and the surfaces of the rolling elements 3 less than 0.51, when the pocket clearance narrows when the claw portions 8 tilt due to centrifugal force, the increase in sliding resistance between the pocket inner surface 11 and the rolling elements 3 is mitigated, and heat generation in the sliding area is suppressed.

[0059] A cylindrical surface 17 that defines the outer diameter of the annular portion 7 is formed on the outer periphery of the annular portion 7. Each of the claw portions 8 has an arcuate surface that is flush with the cylindrical surface 17. The radial gap between the cylindrical surface 17 and the inner periphery of the outer bearing ring 1 is set larger than the aforementioned guiding gap, and the cylindrical surface 17 and bearing ring 1 do not normally contribute to guiding the cage 4.

[0060] The outer diameter variation of the cage 4 is within 600 μm. Here, the outer diameter variation of the cage 4 is the difference between the maximum and minimum values ​​of the actually measured outer diameter obtained over the entire surface of the circular surface that defines the outer diameter of the cage 4. In the illustrated example, the cylindrical surface 17 of the annular portion 7 is the circular surface that defines the outer diameter of the cage 4. By reducing the outer diameter variation of the cage 4 to within 600 μm, the volume distribution near the outer diameter of the cage 4 is well equalized in the circumferential direction, thereby suppressing runout of the cage 4 during rotation.

[0061] The variation in the inner diameter of the cage 4 is within 600 μm. Here, the variation in the inner diameter of the cage 4 is the difference between the maximum and minimum values ​​of the actually measured inner diameter obtained over the entire surface of the circular surface that defines the inner diameter of the cage 4. In the illustrated example, the guide surface 12 of the annular portion 7 is the circular surface that defines the inner diameter of the cage 4. By reducing the variation in the inner diameter of the cage 4 to within 600 μm, the volume distribution near the inner diameter of the cage 4 is well equalized in the circumferential direction, thereby suppressing runout of the cage 4 during rotation.

[0062] The diameter variation of the guide surface 12 of the cage 4 is within 600 μm. Here, this is the difference between the maximum and minimum values ​​of the actually measured inner diameter obtained over the entire surface of the guide surface 12. By reducing the diameter variation of the guide surface 12 to within 600 μm, the amount of radial displacement of the cage 4 caused by the diameter variation of the guide surface 12 sliding against the circumferential surface 10 is effectively suppressed, and therefore runout of the cage 4 during rotation is suppressed.

[0063] The entire cage 4 is made of synthetic resin. Here, the concept of synthetic resin includes a single type of resin, a mixture of two or more types of resin, and a mixture of one or more types of resin as a base material and reinforcing materials (such as glass fiber or carbon fiber) (so-called fiber-reinforced resin). For ball bearings suitable for high-speed rotation, it is preferable to use fiber-reinforced resin.

[0064] Engineering plastics are used as synthetic resins. Engineering plastics generally refer to plastics that have a heat resistance of 100°C to 120°C, a strength of 50 MPa or more, and a flexural modulus of 2.4 GPa or more.

[0065] More specifically, the cage 4 is made of polyamide resin, which is a type of engineering plastic. Examples of polyamide resin include PA, PA6, PA9, PA46, PA66, PA9T+carbon fiber, and PA46 or 66+glass fiber.

[0066] The entire cage 4 is formed by injection molding using a mold (not shown) divided into two parts in the axial direction, injecting synthetic resin from one or more gates in the mold and allowing the injected resin to cool and solidify within the mold. In order to reduce the surface roughness of the pocket inner surface 11 and the mating surface 12 and thereby reduce the aforementioned composite roughness, it is preferable that the corresponding transfer surfaces of the mold be mirror-finished, i.e., have a calculated average roughness Ra of 0.4 μm or less.

[0067] When the surface of the cage 4 is viewed, gate marks, which are cross sections of the synthetic resin sheared when the cage 4 is released, are formed at positions corresponding to the gates.

[0068] As shown in Figure 3, the gates (gate marks) G are arranged on the surface of the cage 4, excluding the pocket inner surfaces 11, the guide surfaces 12, and the back surface 16. In the illustrated example, all of the gates G are arranged on the outer periphery of the cage 4, including the cylindrical surface 17 of the annular portion 7. The outer periphery of the cage 4, including the cylindrical surface 17, is not a part that slides against other bearing components when the rolling bearing rotates. For this reason, even if burrs are formed on the gate marks G on the outer periphery of the cage 4, the burrs on the gate marks G will not rub against other bearing components when the cage 4 rotates.

[0069] The rolling bearing shown in Fig. 1 is suitable for use in supporting a rotating shaft included in a motor or a transmission connected to a motor, for example. An example of this is shown in Fig. 6.

[0070] The rotation transmission device shown in Figure 6 includes a vehicle drive motor 20 and a transmission 30 connected to the motor 20. The transmission 30 includes a plurality of rotating shafts 31-33, gears 34-36 provided on each of the rotating shafts 31-33, and a plurality of rolling bearings 37, 38 supporting the rotating shafts 31, 32, and 33. Rotating shaft 21, which is the motor shaft of the motor 20, is connected to rotating shaft 31, and the two shafts 21, 31 rotate integrally. When the vehicle drive motor 20 serves as a drive source, rotation is input from rotating shaft 21, which is the output shaft of the vehicle drive motor 20, to rotating shaft 31 of the transmission 30, and the transmission 30 functions as a gear reducer that reduces the rotation input to rotating shaft 31 and outputs it from rotating shaft 33. When the vehicle drive motor 20 serves as a regenerative brake, the transmission 30 serves as a gear speed increaser that increases the rotation input to the rotating shaft 33 from the running wheel side and outputs it from the rotating shaft 31 to the rotating shaft 21 of the vehicle drive motor 20.

[0071] Each of the rolling bearings 37 supporting the rotating shafts 21, 31, and 32 is a deep groove ball bearing. The rolling bearing 38 supporting the rotating shaft 33 is a tapered roller bearing. Each of the rolling bearings 37 corresponds to the rolling bearing according to the embodiment shown in FIG. 1 (hereinafter, see FIGS. 1 to 6 as appropriate).

[0072] As described above, this rolling bearing comprises an outer raceway 1 having an outer raceway surface 5, an inner raceway 2 having an inner raceway surface 6, a plurality of rolling elements 3 arranged between the outer raceway surface 5 and the inner raceway surface 6, and a cage 4 that maintains the circumferential spacing of the plurality of rolling elements 3, one of the outer raceway 1 and the inner raceway 2 having a circumferential surface 10 that guides the cage 4, and the cage 4 has a plurality of pocket inner surfaces 11 that hold the rolling elements 3 and a guide surface 12 that is guided by the circumferential surface 10. In particular, since the composite roughness σ of the circumferential surface 10 and the guide surface 12 is 0.7 μm or less and the roundness of the circumferential surface 10 is 30 μm or less, excellent oil film formation ability can be obtained, making it possible to increase the oil film parameter Λ at the sliding portions of both surfaces 10, 12 to 3 or more, even when the rolling bearing is rotating at low speeds.

[0073] In consideration of mass productivity and processability, the composite roughness σ of the guide surface 12 and the circumferential surface 10 is preferably 0.4 μm or more. In consideration of mass productivity and processability, the circularity of the circumferential surface 10 is preferably 5 μm or more.

[0074] Furthermore, in this rolling bearing, the retainer 4 has an annular portion 7 and two or more claw portions 8 that are spaced apart circumferentially and protrude from the annular portion 7 in one axial direction, and the spaces between adjacent claw portions 8, 8 in the circumferential direction form pockets 9 that accommodate the rolling elements 3. Therefore, the sliding area between the guide surface 12 and the circumferential surface 10 is likely to become narrower due to deformation of the retainer 4 caused by centrifugal force, but as mentioned above, excellent oil film formation ability is obtained, so it is possible to prevent oil film deficiency and early damage to the sliding area even when rotating at high speeds.

[0075] In addition, this rolling bearing further includes a locking member 15 arranged in the other axial direction relative to the retainer 4 so as to restrict movement of the retainer 4 in the other axial direction, the annular portion 7 has a back surface 16 that faces the locking member 15 in the axial direction, the annular portion 7 and each of the claw portions 8 are formed integrally by injection molding, and the injection molding gate G is arranged in a portion of the surface of the retainer 4 excluding the guide surface 12 and the back surface 16, thereby shortening the protruding height H of the claw portions 8 and suppressing deformation of the retainer 4 due to centrifugal force.In addition, the retainer 4 is highly suitable for mass production, and even if burrs are generated in the gate marks G, when the retainer 4 is guided by the raceway 2 or the back surface 16 of the retainer 4 with short claw portions 8 is received by the locking member 15 to restrict movement, the burrs in the gate marks G will not rub against the circumferential surface 10 of the raceway 2 or the locking member 15, and this will not become a cause of an increase in the rotational torque of the rolling bearing or noise and vibration.

[0076] Furthermore, when considering the protruding height H of the claw portions 8 in one axial direction relative to the annular portion 7, the difference in protruding height H between each claw portion 8 is within 120 μm, so that even for a claw portion 8 with the maximum protruding height H, the sliding area between its end face portion 13 and the rolling element 3 is not excessively large, and even for a claw portion 8 with the minimum protruding height, the rolling element 3 can be sufficiently held in the circumferential direction.

[0077] Furthermore, in this rolling bearing, the composite roughness σ of the pocket inner surface 11 of the retainer 4 and the surface of the rolling element 3 held in said pocket inner surface 11 is less than 0.51 μm, thereby mitigating the increase in sliding resistance between the pocket inner surface 11 and the surface of the rolling element 3 and suppressing heat generation.

[0078] Furthermore, in this rolling bearing, the variations in the outer diameter and inner diameter of the cage are each within 600 μm, so that runout of the cage 4 during rotation can be suppressed, and therefore vibration values ​​can be reduced.

[0079] Furthermore, because the retainer 4 of this rolling bearing is made of polyamide resin, it is possible to use polyamide resin, which is cheaper than super engineering plastics, as the retainer material, while still making the retainer 4 capable of withstanding use at high speeds.

[0080] Furthermore, this rolling bearing has an oil lubricating retainer 4 with a dynamic viscosity of 50 cst or less at 40°C, which reduces oil agitation resistance inside the bearing, thereby reducing torque loss in the rolling bearing and enabling energy-saving operation.

[0081] The rolling bearing 37 according to the present invention supports the rotating shafts 21, 31, 32 included in the motor 20 or the transmission 30 connected to the motor 20, and as a result has excellent lubrication properties for the sliding parts when the retainer is guided by the raceway, as described above, so that the rolling bearing 37 can be operated with low torque from low speed rotation to high speed rotation, and early damage to the interior of the bearing can be prevented.

[0082] In this embodiment, a deep groove ball bearing is exemplified, but the present invention can also be applied to other bearing types such as angular contact ball bearings and cylindrical roller bearings.

[0083] Furthermore, in this embodiment, a horn-shaped cage is exemplified, but the present invention can also be applied to a squirrel-cage cage.

[0084] In addition, in this embodiment, an example is shown in which the horn-shaped cage and the rolling elements are prevented from separating by a locking member rather than by a claw portion, but this invention can also be applied to a general crown-shaped cage in which the claw portion prevents the rolling elements from separating.

[0085] Furthermore, although this embodiment shows an example in which the entire cage is made of synthetic resin, the present invention can also be applied to cages made of other materials. While it is preferable to make the sliding portions of the cage surface with other bearing components out of synthetic resin from the standpoints of lubricity and aggressiveness, portions of the cage outside the sliding portions may be made of other materials such as metal. For example, for reinforcement purposes, the inside of the annular portion or the outer diameter portions of the annular portion and claws may be made of metal rings, and these metal rings may be inserted into or bonded to the synthetic resin portion.

[0086] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0087] 1 Outer raceway 2 Inner raceway (one of the raceways) 3 Rolling elements 4 Cage 5 outer raceway 6 Inner raceway 7 Annular section 8 Claw 9 pockets 10 Circumferential Surface 11 Pocket interior 12 Guide surface 15 Locking member 16 Back 17 Cylindrical Surface 20 Motor 21, 31, 32 Rotation axis 30 Transmission 37 Rolling bearings

Claims

1. the bearing comprises an outer raceway ring having an outer raceway surface, an inner raceway ring having an inner raceway surface, a plurality of rolling elements arranged between the outer raceway surface and the inner raceway surface, and a cage that maintains the circumferential spacing of the plurality of rolling elements, one of the outer raceway and the inner raceway has a circumferential surface that guides the cage; The cage has a plurality of pocket inner surfaces that hold the rolling elements, and a guide surface that is guided by the circumferential surface, a composite roughness of the circumferential surface and the guide surface is 0.7 μm or less, and a circularity of the circumferential surface is 30 μm or less; The cage has an annular portion and two or more claw portions that are spaced apart in the circumferential direction and protrude from the annular portion in one axial direction, The spaces between the claws facing each other in the circumferential direction form pockets that accommodate the rolling elements, a locking member disposed in the other axial direction relative to the retainer so as to restrict movement of the retainer in the other axial direction; the annular portion has a back surface that faces the locking member in the axial direction, a rolling bearing characterized in that the annular portion and each of the claw portions are integrally formed by injection molding, and the injection molding gate is positioned on a portion of the surface of the retainer excluding the guide surface and the back surface.

2. A bearing comprising: an outer raceway ring having an outer raceway surface; an inner raceway ring having an inner raceway surface; a plurality of rolling elements arranged between the outer raceway surface and the inner raceway surface; and a retainer that maintains the circumferential spacing of the plurality of rolling elements; one of the outer raceway and the inner raceway has a circumferential surface that guides the cage; The cage has a plurality of pocket inner surfaces that hold the rolling elements, and a guide surface that is guided by the circumferential surface, a composite roughness of the circumferential surface and the guide surface is 0.7 μm or less, and a circularity of the circumferential surface is 30 μm or less; A rolling bearing that supports a rotating shaft included in a motor or a transmission connected to a motor.

3. 2. The rolling bearing according to claim 1, wherein when considering the protruding height of said claw portions in one axial direction relative to said annular portion, the difference in protruding height between each of said claw portions is within 120 μm.

4. 4. The rolling bearing according to claim 1, wherein a composite roughness of the inner surface of the pocket of the cage and the surface of the rolling element held in the inner surface of the pocket is less than 0.51 μm.

5. 5. The rolling bearing according to claim 1, wherein the variations in the outer diameter and the inner diameter of the cage are each within 600 μm.

6. 6. The rolling bearing according to claim 1, wherein the cage is made of a polyamide resin.

7. 7. The rolling bearing according to claim 1, wherein the oil lubricating the cage has a kinematic viscosity of 50 cst or less at 40°C.

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